"She is from New York. She is Jewish. She is a woman," wrote one of the graduate programs to which Rosalyn Yalow applied. Their loss: She went on to become the second woman to win a Nobel prize in medicine.

Yalow, who never finished high school, was the first physics major at Hunter College in New York. Her discovery of radioimmunoassay in the 1950s made possible major advances in care related to diabetes, fertility, and thyroid function. As The New York Times describes it,

The test is used, for example, to prevent mental retardation in babies with underactive thyroid glands. No symptoms are present until a baby is more than 3 months old, too late to prevent brain damage. But a few drops of blood from a pinprick on the newborn's heel can be analyzed with radioimmunoassay to identify babies at risk.

She almost didn't get the chance. "They told me that as a woman, I'd never get into graduate school in physics," Yallow recalled, "so they got me a job as a secretary at the College of Physicians and Surgeons and promised that, if I were a good girl, I would take courses there." World War II helped make her first teaching job possible. Even then, it was no easy road:

When she received an A-minus in one laboratory course, the chairman of the physics department at Illinois said the grade confirmed that women could not excel at lab work; the slight fueled her determination.

"We must believe in ourselves or no one else will believe in us...we must feel a personal responsibility to ease the path for those who come after us. The world cannot afford the loss of the talents of half its people if we are to solve the many problems that beset us."